Hardcoded value for validAfter argument could prevent users from initiating a subscription at a later time

function registerSubscription(
  address _subscriber,
  uint256 _amount,
  uint256 _validUntil,
  uint256 _paymentInterval,
  address _erc20Token
) public {
  require(_amount > 0, "Subscription amount is 0");
  require(_paymentInterval > 0, "Payment interval is 0");
  require(msg.sender == _subscriber, "Only the subscriber can register a subscription");

  ISubExecutor.SubStorage memory sub = ISubExecutor.SubStorage({
    amount: _amount,
    validUntil: _validUntil,
    validAfter: block.timestamp,
    paymentInterval: _paymentInterval,
    subscriber: _subscriber,
    initiator: address(this),
    erc20TokensValid: _erc20Token == address(0) ? false : true,
    erc20Token: _erc20Token
  });
}

function registerSubscription(
  address _subscriber,
  uint256 _amount,
  uint256 _validUntil,
+ uint256 _validAfter,
  uint256 _paymentInterval,
  address _erc20Token
) public {
+ require(_validAfter >= block.timestamp, "Sub cannot be valid after a time in the past")
- validAfter: block.timestamp,
+ validAfter: _validAfter,